1. Field of the Invention
The present invention relates to a cathode ray tube, and in particular to a mask frame for a cathode ray tube which is capable of improving howling characteristics and drop characteristics by having an optimum design shape.
2. Description of the Prior Art
In general, a cathode ray tube includes a vacuous vessel consisting of a panel and a funnel. In the cathode ray tube, an electron beam emitted from an electron gun is deflected by a deflection yoke, passes plural electron beam passage holes formed at a shadow mask and lands onto a fluorescent surface formed onto the inner surface of the panel, and accordingly a picture is displayed by each luminescent material of the fluorescent surface.
The cathode ray tube will be described with reference to accompanying drawings.
FIG. 1 is a schematic view illustrating the conventional cathode ray tube.
As depicted in FIG. 1, in the conventional cathode ray tube, a panel 1 as a front glass combines with a funnel 2 as a rear glass, and the internal space is sealed in a high vacuum state.
In more detail, the cathode ray tube includes the fluorescent surface 13 coated onto the inner surface of the panel 1 and performing a certain luminary function; the electron gun 6 installed at the end of the funnel 2 and emitting the electron beam 5; the deflection yoke 7 installed at the outer circumference of the funnel 2 and deflecting the electron beam 5 so as to be scanned appropriate to a size of the fluorescent surface 13; a shadow mask 8 installed at the rear of the panel 1 with a certain distance from the fluorescent surface 13; a mask frame 9 for supporting the shadow mask 8; and an inner shield 10 installed lengthily from the panel side to the funnel side and preventing color purity deterioration due to magnetic filed influence by shielding outer earth magnetism.
The panel 1 has an almost rectangular shape. And, it consists of an effective portion 3 having the fluorescent surface 13 formed at the inner surface and a skirt portion 4 projected from the circumference of the effective portion 3 and combined with the funnel 2.
A spring supporter 14, at which a support spring 11 for elastically supporting the mask frame 9 to the panel 1 is fixed, is installed inside the skirt portion 4 of the panel 1, and a reinforcing band 12 is installed around the outer circumference of the skirt portion 4 of the panel 1 in order to reinforce the combining outer circumference between the panel 1 and the funnel 2.
As depicted in FIG. 2, the mask frame 9 includes a rectangular opening 21 formed at the inner surface to pass the electron beam 5; a bottom portion 24 consisting of two long side bottoms 22 and two short side bottoms 23; and a side portion 20 vertically extended from the bottom portion 24 to mount the shadow mask 8.
An inner shield combining hole 28 is formed at the bottom portion 24 to combine the inner shield 10 with the mask frame 9.
And, a stair-shaped bead 27 is respectively formed at regular intervals at a portion at which the bottom portion 24 meets the side portion 20 in order to improve strength of the mask frame 9.
The side portion 20 is classified into two long sides 25 and two short sides 26 according to a length, and each side is connected with each other by forming a corner portion 29.
In the above-described cathode ray tube, according to comparative increase of a width of the cathode ray tube, it is difficult to secure an installation space. In addition, a weight of the cathode ray tube is increased.
In more detail, with a recent slim-lightweight trend in cathode ray tube, using a method for reducing a width of the skirt portion 4 of the panel 1 can be considered to slim down the cathode ray tube.
In more detail, as depicted in FIG. 3A, the skirt portion 4 of the panel 1 can be reduced as a certain width (xcex94W). Herein, in a minimum total length of the cathode ray tube in consideration of a deflection angle of the electron beam 5, a size of the skirt portion 4 of the panel 1 can be reduced within the range of 10xcx9c15 mm.
However, as depicted in FIG. 3B, when the conventional mask frame 9 is applied as it is to the panel 1 having the reduced skirt portion 4, because a margin between the end of the mask frame 9 and the inner surface of the panel 1 is decreased, mutual interference may be occurred, by the interference, in fabrication process of the cathode ray tube, the panel 1 may be scratched or damaged.
Accordingly, in order to prevent the interference, a height of the side portion 20 of the mask frame 9 is reduced, by the height reduction of the side portion 20, because an area of the combining surface of the shadow mask 8 and the mask frame 9 is reduced, a combining force is lowered, and accordingly howling characteristics and drop characteristics of the shadow mask 8 may be deteriorated.
Accordingly, in order to apply the skirt portion 4 of the panel 1 to the reduced cathode ray tube appropriately, designing an optimum mask frame shape which is capable of satisfying howling characteristics and drop characteristics of the shadow mask 8 is required.
In order to solve the above-mentioned problem, it is an object of the present invention to provide a mask frame for a cathode ray tube which is capable of preventing interference between the inner surface of a panel and a mask frame due to decrease of an interval between them according to sliming-down of a panel and improving howling characteristics and drop characteristics of the cathode ray tube by having an optimum shape.
In order to achieve the above-mentioned object, in a cathode ray tube comprising a panel having a fluorescent surface coated onto the inner surface, a funnel connected to the panel, a shadow mask installed with a certain interval from the fluorescent surface; and a mask frame for supporting the shadow mask, a mask frame for a cathode ray tube satisfies following equation 0.80xe2x89xa6a/(Xd/4)+b/(Yd/4)+c/(Dd/4)xe2x89xa61.25, wherein Xd is a long side length of the mask frame, Yd is a short side length thereof, Dd is a diagonal length thereof, a is a height of the center of the long side thereof, b is a height of the center of the short side thereof, and c is a height of the corner portion thereof.